BAK Batteries

Did a rundown of some BAK batteries from Xeccon. From my understanding, there are even different grades of new BAK batteries. BAKs in Xeccon and Magicshine batteries should be the same grade, but I cannot confirm that. My feeling is, the Xeccon ones are slightly better.

All batteries in this rundown are Xeccon supplied BAK batteries. The set up and results:

Time lapse@30 secs on the Replay XD record which light done what when. The purpose of this test was to subject the batteries to various draw currents including overloading them with 2 light heads' draw. Surprise result was how long the MJ-872 went for. [EDIT: Wrong diagnosis. The problem was not over-discharge protection just bad coincidence - there was a weak solder joint with this battery.] The battery will not charge with the broken circuit but will the moment a finger is used to push the connections back together. [EDIT: This unusual solder failure is fully covered by warranty.]

So not all is lost in an emergency if your battery suffers a protection cut out in the woods. The good question is, even in a normal low battery shutdown deep in the woods (with a pen light to work), are you able to by-pass the circuit to give you "reserve" power? It will damage the batteries no doubt but life is priority. How much longer will it go for?

BAK cells from Xeccon are easy to identify. The wrappers are Aqua Blue with "BAK A 02" and a barcode printed on. Build quality is good. Inter-connections and finishing is also quite good. My only concern is there are no rubber or silicone boot for 6600mAh batteries to date. Hope to have this remedied soon. Currently, to ensure further waterproofing, suggest using duct tape to seal up the battery completely before putting it into the neoprene pouch.

I was going to tear up the battery pack and show the cells in the raw then noticed the protection circuit can be remedied for my personal use. If anyone wants me to go that step further, let me know. I will sacrifice it.

Part 2

Someone has to teach me how to take draw current readings. In the meantime, I will borrow data from Jim Harger of Action. Thanks Jim, and if that's not sufficient, I took your data because treat you as the authority in these matters.

In his chart, the MJ-808E draws 1.48A. There are other readings elsewhere with about 1.5A. Either the drivers or instruments have variations, I would think probably both. The MJ-880 standard with T6 is 2.8A. Runtimes for 2 x 808E and the single MJ-880U is just 3 mins difference in this test - the gap may be more or less in another test, in my experience. Just have an inkling the draw on the MJ-880U is even higher. The heat produced is something else.

[EDIT: Removed Protection Circuit statement. Not relevant] I did this test with the 808Es because TiGeo mentioned he may want to get another 808E and share a larger capacity battery. Suggest running them independently like the S12s my lid. On the bar I use a Y cable since they aren't used much.

The MJ-872 on the other hand seem to have drawn less than usual. 4 hours 30 is not something I expected. Was it truly drawing at 2.2A according to the chart? I am ending up with more questions than answers.

Magicshine's Samsung & BAK cells

While we're on a roll here let's not hide behind boots and shrink wraps. Since I mentioned I have a feeling the Xeccon BAKs are different to MS's BAKs, I decided to confirm this for the first time. The Lime Green wrappers are different for one. No mention of BAK on the MS cells anywhere [edit:] that I can see.

Since the MJ-6030 5600mAh has been mentioned in recent post, why not compare that too? The light purple wrappers on the Samsung cells are clearly marked as such.

On the outside, there is no visible difference between the MJ-6002 and MJ-6030. Remove the silicone boot, there's STILL no difference. Remove the black shrink wrap then you see true colors. Protection boards also seem to be the same for both so that may mean the cells are ordered by bulk and assembled in a common place.

Will do a cross-rundown test when I get the time. This means crossing the chargers to ensure extra or reduced runtime is not from a rogue charger.

Attached Thumbnails

Last edited by mtbRevolution; 12-03-2012 at 12:42 AM.
Reason: The printed BAK may be on the underside. Cannot confirm unless I pull it apart.

Interesting post Len. To me it sounds like the PCB in the battery had a bad connection or that the PCB itself is not designed to handle the high current drawn by the two 808E's in parallel. ( should be close to 3A ). Could be the solder on one wire melted when the board got hot. Hard to know for sure but I do know that when you buy batteries from a reputable battery store they always list the maximum output current a battery PCB will handle.

Obviously the 6 cell battery could handle the current or the battery would of shut down immediately. Likely I think this is just a case of a bad PCB. If you replace the board the battery will likely work fine. I am assuming though that like most PCB's used for battery protection this one includes a circuit that will shut down the battery if the output current exceeds the manufacturer's listing.

Back in the old days of halogen lamps we use to try to over-volt our lamps by using higher voltage Li-ion batteries ( this made the bulbs brighter ). Depending on where you got your batteries from this would sometimes work without problems. On the other hand if the battery had a low current limit, the initial surge current when first turned on would trigger the battery PCB to shut down. We used to by-pass this problem by pulsing the on/off switch till the bulb fired up. We used to call this "Ghetto starting". It worked but was a real PITA to deal with. Of course if you have a battery with a higher set current limit than there was no problem.

**correction: the 808E draws 1.5A on high. Two in parallel 3A. I corrected the number above which was 5A. At 3A the battery shouldn't of had a problem.

Interesting post Len. To me it sounds like the PCB in the battery had a bad connection or that the PCB itself is not designed to handle the high current drawn by the two 808E's in parallel. ( should be close to 3A ). Could be the solder on one wire melted when the board got hot. Hard to know for sure but I do know that when you buy batteries from a reputable battery store they always list the maximum output current a battery PCB will handle.

Obviously the 6 cell battery could handle the current or the battery would of shut down immediately. Likely I think this is just a case of a bad PCB. If you replace the board the battery will likely work fine. I am assuming though that like most PCB's used for battery protection this one includes a circuit that will shut down the battery if the output current exceeds the manufacturer's listing.

**correction: the 808E draws 1.5A on high. Two in parallel 3A. I corrected the number above which was 5A. At 3A the battery shouldn't of had a problem.

Agreed that 3A should not be a problem. Personally I don't like stressing the batteries this way but it's a test.The runtime for a single 808E is about 3 hours 15 mins from a 4400 @ ~1.5A draw. So to get 2 hours 27 mins from them running parallel is pretty good I thought. They were quite stable - normally you'll see them yo-yo between 2 indicator colors. So based on the rundown time, one would expect it to be close to total depletion. What are the chances of being close to total depletion and the PCB solder failing then? That is what stumped me. I thought it was a over-discharge protection. Posted this anyway whether it's a good or bad thing since it happened. If it's the solder and hence a manufacturing fault, it's under full warranty.

Thanks for sharing your experience with the batteries. I would agree with Cat. The broken connection had nothing to do with any kind of "over-discharge" protection. It was likely just a poor solder joint to begin with, weakened by excessive heat. It's a bit of a "positive feedback" scenario. The bad solder joint can have higher resistance, and thus generate more heat, which weakens the joint, which causes more resistance, which causes more heat... well, you get the idea.

The other thing to remember about li-ion cells is that they have extremely predictable discharge behavior. The biggest thing you can learn about about a particular battery is whether or not it's actually delivering the rated capacity. Your tests with the 808E at least suggest that the two packs were similar.

Start with the first test case with the 808E and the 4400 maH. Since you don't know the current exactly, you have the next best thing... the time. Also remember that the current draw will not be constant over the discharge cycle, so the best you can do is state an "average" current draw over the full discharge cycle.

So it looks like you did get a full test that probably stopped normally (i.e. at the correct discharge voltage). I suppose it's possible that the solder joint failed and that it continued running simply because the shrink wrap was pressing it into contact with the board. You should just solder it back and see if you can still re-charge.

The PCB board that you show in the picture is super-minimal. It's basically just a couple of power MOSFETS that get turned off when the voltage drops below a prescribed limit determined by a resistor divider.

The bigger concern for the life of these packs is the fact that the PCB does not have a "balancing" function, whereby each individual cell's voltage is balanced to the same value during charging. Otherwise, over time, some will drift high and some will drift low. Eventually, you end up with some cells overcharging and some cells over discharging, even though the pack voltage is still correct. Once the low cells start crossing into the overdischarge range (less than 2V per cell), the pack is pretty much done. The more expensive packs will have balancing along with many more safety functions, which can contribute to a longer life.

Xeccon BAK vs MS BAK vs MS Samsung

Originally Posted by pethelman

Thanks for sharing your experience with the batteries. I would agree with Cat. The broken connection had nothing to do with any kind of "over-discharge" protection. It was likely just a poor solder joint to begin with, weakened by excessive heat. It's a bit of a "positive feedback" scenario. The bad solder joint can have higher resistance, and thus generate more heat, which weakens the joint, which causes more resistance, which causes more heat... well, you get the idea.

The other thing to remember about li-ion cells is that they have extremely predictable discharge behavior. The biggest thing you can learn about about a particular battery is whether or not it's actually delivering the rated capacity. Your tests with the 808E at least suggest that the two packs were similar.

Start with the first test case with the 808E and the 4400 maH. Since you don't know the current exactly, you have the next best thing... the time. Also remember that the current draw will not be constant over the discharge cycle, so the best you can do is state an "average" current draw over the full discharge cycle.

So it looks like you did get a full test that probably stopped normally (i.e. at the correct discharge voltage). I suppose it's possible that the solder joint failed and that it continued running simply because the shrink wrap was pressing it into contact with the board. You should just solder it back and see if you can still re-charge.

The PCB board that you show in the picture is super-minimal. It's basically just a couple of power MOSFETS that get turned off when the voltage drops below a prescribed limit determined by a resistor divider.

The bigger concern for the life of these packs is the fact that the PCB does not have a "balancing" function, whereby each individual cell's voltage is balanced to the same value during charging. Otherwise, over time, some will drift high and some will drift low. Eventually, you end up with some cells overcharging and some cells over discharging, even though the pack voltage is still correct. Once the low cells start crossing into the overdischarge range (less than 2V per cell), the pack is pretty much done. The more expensive packs will have balancing along with many more safety functions, which can contribute to a longer life.

Thanks Stephen. Always great to hear you explain these things. Yes, Cat and you are correct. Got confirmation from Xeccon's engineers yesterday it was a bad solder in this rare case - no failure, till now. The solder joint with this battery was just at the top left hand corner of the contact point hence higher resistance as you stated. I should know better than to assume it was over-discharge. Lesson learnt.

Xeccon Light consider this a warranty issue so we got a credit. Will suggest PCB upgrades with them.

Can we also get a definitive answer, using a Y cable should not stress the batteries more and there is no extra resistance doing so? I noticed in the past it makes the color indicators change earlier than usual and sometimes yo-yo back and forth.

Back to the Xeccon BAK vs MS BAK vs MS Samsung. I did another series of rundown test. This time, using the same charger and MJ-808E light head, one at a time. Any reading difference should be from the batteries not the charger, light head, temperature of 19°C and fan position since they are common denominators in this test. The same batteries are doing 2 rundowns each.

You are right, again by stating Li-ion packs are quite predictable. They seem to be consistent with the depletion time when the other factors are the same. I did however notice the color indicators changes are not as uniform - can fluctuate up to 8 mins. Noticed this too from the other test I've done to date.

Decided to use the 808E light head for this test because it's common and most can relate to it. In this test, the MJ-6002 had less than average runtime.

I would note that its to be expected to see a very wide fluctuation in the colored battery status indication. From about 30% to 90% discharge, the voltage curve is pretty flat (nice characteristic of the li-ion), but it makes it exceedingly difficult to precisely determine where you are on the discharge curve. Just that tiny bit of extra resistance in the Y-cable is more than enough to affect the function of the voltage sensing.

During the flat part of the discharge curve, a normal 0.1-0.2V drop in battery voltage can translate into a fairly significant amount of time. If you're pulling 1.4 amps, and you add even 1/10th of an ohm into the circuit (completely reasonable for a Y-cable), you just dropped the voltage sensed by the circuit by 0.14V, which could easily be enough to change the status LED if you were already close to the threshold.

What's really fun is when you start running multiple lights off of the same battery, with one flashing and one not. Talk about confusing the battery status indicator. I have a 0.4V hysteresis built into mine just for such an occasion.

At first I was like 'no big deal' then it dawned on that each battery is powering
TWO magicshine lights....
Thats pretty dam cool! My geoman replacment pack runs my old MS for 2:30 or so
Maybe instead of building a Keeppower pack I'll just buy one of these!
CDT

BAK cells

The stripped-pack was used running 4 x 808Es in 4 rundowns via 3 Y cables. We did this to test the cells in this particular pack. The cells performed well but IMO and others battery pack can be improved with higher rated and better PCB.

Results of the rundowns were, 29 mins, 33 mins, 32 and 35 mins. Time lapse recorded for all runs done.

This test is done in the interest of showing the durability of the BAK cells but loading batteries this way is not recommended. At the end of each run the battery pack was a touch warm. Battery recharged as per normal after each test.

This hours and mins to decimal converter is handy for draw calculations.

Hi Leonard,
I ran through a battery cycle this week with my 6600 Xeccon to familarize myself with how it would perform using a y-cable and two lightheads. The set-up used was a Titan run on high for the front and a Titan w/red wide angle lens run on low as a tail light. Taking the ride time off my cateye (3hrs 24min) and it ran another 30 min (approx.) in front of a fan before it shut itself off. I'm assuming the battery shut the lights off since I never noticed power level LED on the lighthead turn red. There was still enough power in the battery to run the lights on a lower setting but I stopped there sinse I just wanted an approx runtime for this set-up. Interesting that using it with my olympia lighthead it ran down to flashing red, using y-cables you never know what to expect. Anyway, approx 4 hr runtime is perfect for a couple of after dinner rides for me!
Mole

This looks interesting. I'm using one single 808 clone in the bars when commuting with angle lens but i think it is not sufficient. As i'm in a tight budget, i might get an Y cable + that 6600 battery from Xeccon + a real magic shine 8083 and apply another angle lens to it. What do you think? I don't know how much amps my clone pushes, but judging from runtime and comparing with those 1.5A from MS i guess it will be pretty much be the same thing. If it does not, it wont really be a problem, right?

Xeccon, I checked your site and i can see there is a promotion to mtbr members, but i can see the price is higher (49$ vs 45$). Am i missing something? I'm from Portugal, so it would be nice to get a discount or even find another dealer, as the shipping cost is way to expensive (almost 50% the cost of the product).

This looks interesting. I'm using one single 808 clone in the bars when commuting with angle lens but i think it is not sufficient. As i'm in a tight budget, i might get an Y cable + that 6600 battery from Xeccon + a real magic shine 8083 and apply another angle lens to it. What do you think? I don't know how much amps my clone pushes, but judging from runtime and comparing with those 1.5A from MS i guess it will be pretty much be the same thing. If it does not, it wont really be a problem, right?

Xeccon, I checked your site and i can see there is a promotion to mtbr members, but i can see the price is higher (49$ vs 45$). Am i missing something? I'm from Portugal, so it would be nice to get a discount or even find another dealer, as the shipping cost is way to expensive (almost 50% the cost of the product).

Hi Pedro, we will work something out with the product and shipping cost as discussed on Live Help. Understand you want to use your wide angle lens so best option right now is the S14 U2 with 6600 and a Y cable if I can get you one from our China office. Using the S12 U2 with wide angle lens just defeats the whole purpose of buying that real thrower light.

Best suggestion is, keep your clone and current battery for bar duties and the S12 on the helmet. Beamshots of the S12, S14 or other lights are in our blog.

Thank you Leonard!
I must decide now what to do with my current setup and what i really need. I don't like the light on the helmet, because i will be using it only exclusively on the road, so i'm looking for a good flood instead of throw.

I saw the Geinea I Micro beamshot photo and i think it is what i need. It looks great for road and commuting... However, we are paying more for this light due to the size of it, right? Would i be best served with both S14 + 808 clone with wide angle lens in the bar?

Bak msds

Li-ion batteries which travel by air in numbers must have a MSDS or Material Safety Data Sheet. This document must be kept on file should information on the batteries are required in an emergency. I am posting this to give you a better insight into new Li-ion batteries. Material/ components/ ingredients are listed in percentages.

It's just a little wee bit harder to export Li-ion batteries from China now because there was a venting incident in a plane a few weeks ago causing stricter Li-ion compliance and further export disruption. We still don't know who the culprit was.

ps. Will continue with more battery test after this. Pedro has been answered on PM.

Mr Mole: Great to hear the batteries are working out for you as with others. We are running low on stock for the mtbr battery specials. I have asked Faye if they would like to extend it.

The bigger concern for the life of these packs is the fact that the PCB does not have a "balancing" function, whereby each individual cell's voltage is balanced to the same value during charging. Otherwise, over time, some will drift high and some will drift low. Eventually, you end up with some cells overcharging and some cells over discharging, even though the pack voltage is still correct. Once the low cells start crossing into the overdischarge range (less than 2V per cell), the pack is pretty much done. The more expensive packs will have balancing along with many more safety functions, which can contribute to a longer life.

to be fair, I've not seen a bike light battery tear down from any of the big name brands (Lupine, NR, L&M) that has a balancing PCB. They're really quite big with noticeable extra bits to burn off small voltage differences during charging. There might be other types which are smaller, but I couldn't find any when I spent some time checking them out for my next build as it would be really neat to drop the balance port cable.

The high end manufacturers make their batteries last a long time just by using quality matched cells that are assembled properly - the Samsungs would definitely fall under the quality cell label.

To Leonard - the best test of a battery's quality that I know off is a high amp (1C minimum) discharge, followed by a charge and self-discharge test of at least a week. Good quality cells should be able to sustain a 1C discharge with only a 10-15% loss in capacity and not noticeably self-discharge over a week. Crap cells can't even cope with a 0.5C discharge without sagging to cut off point. The MS lights and the like can get around this by using 2P packs, so that each cell is only providing 0.25-0.3C.

to be fair, I've not seen a bike light battery tear down from any of the big name brands (Lupine, NR, L&M) that has a balancing PCB. They're really quite big with noticeable extra bits to burn off small voltage differences during charging. There might be other types which are smaller, but I couldn't find any when I spent some time checking them out for my next build as it would be really neat to drop the balance port cable.

The high end manufacturers make their batteries last a long time just by using quality matched cells that are assembled properly - the Samsungs would definitely fall under the quality cell label.

To Leonard - the best test of a battery's quality that I know off is a high amp (1C minimum) discharge, followed by a charge and self-discharge test of at least a week. Good quality cells should be able to sustain a 1C discharge with only a 10-15% loss in capacity and not noticeably self-discharge over a week. Crap cells can't even cope with a 0.5C discharge without sagging to cut off point. The MS lights and the like can get around this by using 2P packs, so that each cell is only providing 0.25-0.3C.

Thanks for your input Matt. We welcome any suggestions to make the batteries better. These tech stuff is out of my league. I would like to send you a 6600mAh for your thoughts, review and suggestions. PM you in a moment.

Reversed Y Cable

The test done today is probably more about the reversed Y cable than the batteries. I have a couple of these Y cables from my old Cateye halogens. They are meant to Y junction two cylindrical batteries together to a switch then branch off to 2 lights. I bought 2 sets back then - needed a 25w on the helmet and 25 + 10w on the bars, the other 10w ended up as a spare. Believe it or not, it was quite serious firepower in those days. Vistalite 5w was da-light to buy then...

Back on track. Since the male/female connectors are reversed and compatible with Xeccon/MS/Inton connectors, I am able to do a couple of test with it.

First test is running 2 x Xeccon 4400 batteries via this reversed Y to a single S12 U2. The second set is a S12 U2 with a single 4400. All test I do is conducted on Hi or max brightness.

Connecting 2 batteries to a single light head just doubled the runtime + a bit. Two reason for this, + a bit. (A). The single battery runtime is less than usual. (B). The S12 powered by 2 batteries were slightly dimmer than the single battery set up. However, I observed the opposite with the Inton NB-04 when connected to 2 batteries - not sure if you can see it from the pics posted below.

In essence there was no real benefit connecting 2 batteries to a single light head IMO. Note: the two batteries can be charged simultaneously using 1 charger if this Y is available.

The stripped-pack was used running 4 x 808Es in 4 rundowns via 3 Y cables. We did this to test the cells in this particular pack. The cells performed well but IMO and others battery pack can be improved with higher rated and better PCB.

Results of the rundowns were, 29 mins, 33 mins, 32 and 35 mins. Time lapse recorded for all runs done.

Could you tell me how this 4x808E configuration is comparable to use of one 4 x XM-L light (like Skyray J58)?

I am aware that battery pack that comes with this Skyray (4 cell - 4400mAh claimed) if far from enough for such a powerful light, so I think about buying Xeccon 6600mAh battery or making myself of 6800mAh (4 x Panasonic 18650B- 3400mAh) or 10200mAh (6 x Panasonic 18650B - 3400mAh) packs. What would be most reasonable? I would be grateful for any advice, as my experience in this matter is close to none.

Could you tell me how this 4x808E configuration is comparable to use of one 4 x XM-L light (like Skyray J58)?

I am aware that battery pack that comes with this Skyray (4 cell - 4400mAh claimed) if far from enough for such a powerful light, so I think about buying Xeccon 6600mAh battery or making myself of 6800mAh (4 x Panasonic 18650B- 3400mAh) or 10200mAh (6 x Panasonic 18650B - 3400mAh) packs. What would be most reasonable? I would be grateful for any advice, as my experience in this matter is close to none.

Hi freebird, it's not comparable since in this test the 4 lights are drawing 1.35A average x 4 = 5.4A draw. I do not know the draw of the Skyray J58 but I can't imagine it being over 2.5A. Need runtime or specified current draw to calculate with the battery capacities. The current draw for a particular 3 x XM-L light is only 2.03A so if I had to guess, a 4 x XM-L light will most probably be around 2.3A

I can't tell you if building a 10,200mAh pack from 6 x Panasonics will be reasonable. We do not know the final cost in a custom build. Matt should be able to give you an estimate. What we do know is, the Xeccon 6600 is at USD 49 delivered in the US while the Gloworm 5800mAh 4 cell pack is USD80 currently at Action LED. The Xeccon BAKs have so far been proven to be stable and consistent.